It is frequently desirable to read, by machine, a serial number present on an article. The serial number may be two-dimensional and applied by standard printing techniques, or may be three-dimensional. In the latter case, the serial number may be engraved, embossed, stamped, machined, laser-etched, or otherwise applied. In many of these latter cases, subsequent handling and processing of the article can damage the serial number. For example, a gas turbine engine blade can be laser-etched with a serial number. Subsequently, the blade can be shot-peened to reduce surface stresses. The shot-peening has an unwanted side effect of distorting the edges of the serial number, making the number difficult to read, especially when using optical character recognition (OCR) equipment.